advanced cutting edge research...

先進情報科学特別講義Ⅱ,ⅣADVANCED CUTTING EDGE RESEARCH SEMINAR II, IV

高スループット無線通信システムに関する研究動向

Research Trends on High Throughput

Wireless Communication Systems

Lecture ４

Tran Thi Hong

Computing Architecture Lab

Room: B405

1

LECTURE INFORMATION

Lecturer

Assistant Prof. Tran Thi Hong, Computing Architecture Lab

Slide

I will upload lecture slides here: http://arch.naist.jp/~hong/

Score

Contact

Room: B405

Email: [email protected]

Pass (合格） Attend at least 3 classes

Ｏｒ，2 classes + Active

Not Pass （不合格） Attend less than 3 classes

http://arch.naist.jp/~hong/

LECTURE CONTENTS

Lecture 1+2: Fundamental of Communication System

Lecture 3+4: Research Trends on High Throughput

communication systems

3

RESEARCH TRENDS ON HIGH THROUGHPUT

COMMUNICATION SYSTEM (2)

4

LECTURE CONTENTS

WiFi: High Efficient Wireless HEW 802.11ax

Cognitive Radio

Massive MIMO

Miliwave Communication

LiFi Communication

Appendix: MAC Layer

5

MASSIVE MIMO (1)

Massive MIMO is a communication system that the

base station uses a large number of antennas

(hundreds, thousands) for transferring data.

6

MASSIVE MIMO (2)

7

MASSIVE MIMO (3)

8

MASSIVE MIMO (4)

Challenges:

The complexity in channel estimation increases with

increase in the number of antennas.

Loop interference increases with increase in the spatial

antennas.

Training symbols for channel estimation depends on the

number of transmitting antennas. Increase in number of

training symbols decreases overall throughput.

Etc.

9

10

L: Legacy

HT: High Throughput

STF: Short Training Field

LTF: Long Training Field

SIG: Signal field

L-STF L-LTF DATAL-SIG

4us8us8us 8us

HT-SIG HT-STF

4us

HT-LTFs

4us per LTF

Legacy mode (11a/g compatibility)

Mixed mode (High Throughput mode)

L-STF L-LTF DATAL-SIG

4us8us8us

HT-

STF1

4us

HT-

STF2

4us

HT-

STF3

4us

HT-

STF4

4us

MASSIVE MIMO (5)

MILLIMETER (MM) COMMUNICATION (1)

Wireless Communication that uses the EM wave

in the range 1mm to 10mm wavelength (30 – 300

GHz).

11


Characteristics of mm waves:

Narrow beam width

Large attenuation

12

13

Ref: Naoya Kukutsu et al., Overview of Millimeter and Terahertz Wave

Application Research, NTT


14

Ref: Prasanna Adhikari, Understanding Millimeter Wave

Wireless , White Paper, Loea Corporation, San Diego


𝐿𝑃=10× 𝑙𝑜𝑔10∆𝑃

𝑃

𝐿𝑃: 𝐿𝑜𝑠𝑠 𝑜𝑓 𝑝𝑜𝑤𝑒𝑟 𝑑𝐵∆𝑃: 𝐿𝑜𝑠𝑠 𝑜𝑓 𝑝𝑜𝑤𝑒𝑟 𝑚𝑊

𝑃: 𝑇𝑟𝑎𝑛𝑠𝑚𝑖𝑡𝑡𝑒𝑑 𝑝𝑜𝑤𝑒𝑟 (𝑚𝑊)

15




𝐿𝑃=10× 𝑙𝑜𝑔10∆𝑃

𝑃

𝐿𝑃: 𝐿𝑜𝑠𝑠 𝑜𝑓 𝑝𝑜𝑤𝑒𝑟 𝑑𝐵∆𝑃: 𝐿𝑜𝑠𝑠 𝑜𝑓 𝑝𝑜𝑤𝑒𝑟 𝑚𝑊

𝑃: 𝑇𝑟𝑎𝑛𝑠𝑚𝑖𝑡𝑡𝑒𝑑 𝑝𝑜𝑤𝑒𝑟 (𝑚𝑊)


Characteristics of mm waves:

Narrow beam width

Large attenuation

Easy to be absorbed by thick wall.

Interference with oxygen and rain.

16

PT : Signal power at TX

PR : Signal power at RX

GT : Gain of TX antenna

GR : Gain of RX antenna

r : distance from TX to RX

λ : wavelength of carrier signal

Advantages

Large available bandwidth high data rate

70GHz -> 80 GHz : 10 GHz > Total licensed spectrum

currently

Narrow beam + large attenuation

Reduce interference

Spectrum reused is good

17


Advantages

High security

High frequency small antenna

Reduce chip size

Increase number of antennas (array smart antenna)

increase data rate.

18


Disadvantages

High cost on manufacturing

Large attenuation need high gain antennas

Wall-blocked, interference by oxygen, rain difficult

for long distance communication

19


20




Application:

Metro Network Service

21

Ref: http://www.wimax-industry.com/sp/htn/htnxhl3.htm


Application:

Cellular / WiMAX Backhaul

http://www.wimax-industry.com/sp/htn/htnxhl3.htm

Application:

Cellular Distributed Antenna System (DAS)

22Ref: Prasanna Adhikari, Understanding Millimeter Wave



LIFI COMMUNICATION

Light Fidelity (Li-Fi) is a form of visible light

communication (VLC)

It uses light from light-emitting diodes (LEDs) as

a medium to transfer data

VLC works by switching the current to the LEDs

off and on at a very high rate, too quick to be

noticed by the human eye

23

24Ref: Nitika Bansal et. al, LiFi Technology:

Next Generation Wireless Technology, J. of

Latest Trends in Eng. And Tech. , 2015

LIFI COMMUNICATION (2)

How it works

If LED is on send 1

LED is off send 0

Advantage:

High data rate

Lighting + transferring data ( 2 in 1)

No electromagnetic wave safety environment

High security

Can be used undersea

25


Disadvantage:

Need light

Cannot penetrate wall the signal is blocked inside

room or building.

Should be Line of Sight (LoS)

Interference with other light source and sunlight

Multipath distortion problem

26


27


Applications:

28


Applications:

29


Applications:

30


Applications:

31


Applications:

SUMMARY

OFDM, Cognitive Radio : use the current limited

spectrum resource effectively

MIMO, MU-MIMO, Massive MIMO: increase the

spatial streams

Millimeter wave communication: seek for new

spectrum resource for communication

LiFi : Open a new wireless communication technology

without using radio wave 32

APPENDIX : MAC LAYER

Tran Thi Hong33

INTRODUCTION

Link Layer: includes 2 sublayers

Logical Link Control (LLC): provides frame

communication service with flow & error control

Medium Access Control (MAC): access control to the

wireless shared medium

MAC protocols can be classified into two types:

Contention free: predefine assignment so that

stations can transmit without contending for medium.

Ex: polling, reservation, TDMA, FDMA, etc.

Contention-based: station contends for medium

access. Ex: ALOHA, CSMA, MACA, MACAW, FAMA,

CSMA/CA, CSMA/CD, etc. 34

ALOHA

The first wireless communication system, setup at Hawai islands, 1971

Station send data as soon as there is data

station AP

Data

No error

• If no-reception of ACK within a predefined time T collision resend after random time

• Simple, BUT Low Effective

collision

35

CARRIER SENSE MULTIPLE ACCESS

(CSMA)

Sensing the medium before sending data to reduce collision

If no-reception of ACK within a predefined time T collision resend

station AP

Data

No error

Channel

is IDLE

• Hidden Node problem: happen when a station does not hear the signal from other stations channel sensing is not correct collision

• Ex: S-A and S-B want to send data to AP S-B does not hear signal from S-A S-B may send data to AP while S-A is sending collision

S-A

AP

S-B

collision

36

MULTIPLE ACCESS WITH COLLISION

AVOIDANCE (MACA)

Try to solve Hidden Node Problem

Use RTS/CTS ( Request-To-Send, Clear-To-Send) commands

station AP

Data

No error

RTS frame << DATA frame

RTS frame contains the DATA frame length information.

S-A

AP

S-B

collision

Wait..!

37

FAMA: FLOOR ACQUISITION MULTIPLE

ACCESS

Using: Carrier sensing

RTS/CTS frame exchange

Time intervals: fixed values defined by standards

Station

AAP

Station

B

collision38

FAMA: FLOOR ACQUISITION MULTIPLE

ACCESS

Station

AAP

Data

Station

B

Time

intervals

What is the optimal time interval?

need a lot of researches

39

CSMA/CA: CARRIER SENSING MULTIPLE

ACCESS WITH COLLISION AVOIDANCE

Carrier sensing

Interframe space

RTS/CTS (optional)

Random back-off time

Station

AAP

Data

Station

B

Time intervals

= inter-frame space

+ random back-off time

40

THE END OF LECTURE!Tran Thi Hong41

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